High-frequency heating equipment

ABSTRACT

A high-frequency heating equipment in which a high-frequency generator is stopped when the handle of a door of a heating chamber is touched or grasped upon opening the door, thereby avoiding high-frequency waves from leaking out through a port of the heating chamber, thus preventing any accident imparting an impediment to the human body and simultaneously preventing any interference to other communication appliances.

O Unlted States atent 1 91 1 11 3,715,553 ()gawa et al. 1 Feb. 6, 1973[541 HIGH-FREQUENCY HEATING 3,281,567 10/1966 Meissner et a1. ..21910.55 EQUIPMENT 2,595,748 5/1952 Andrews ..2l9/10.55 2,896,131 7/1959Schumann... .....200/D[G. l [75] Invemms? 03a; 2,320,462 6/1943 Nawells..200/1510. 2 of Nara Japan 1,657,459 1/1928 Davis ..200/1310. 2 [73]Assignee: Matsushita Electric Industrial Co.

Ltd., Oaza Kadoma, Kadoma-shi, Primary Examiner-R. F. Staubly \Osaka,Japan Assistant Examiner-Hugh D. Jaeger [22] Filed: June 25, 1970Att0rney-Stevens, Davis, Miller & Mosher [21] Appl. No.: 49,624 [57]ABSTRACT A high-frequency heating equipment in which a highl l ForeignApplication Prlomy Data frequency generator is stopped when the handleof a July 3, 1969 Japan ..44/53623 door of a heating chamber is touchedor grasped "P opening the door, thereby avoiding high-frequency [52]U.S. Cl ..219/10.55, ZOO/DIG. 1 waves from leaking u through a port ofthe heating [51] Int. Cl ..l-l05b 9/06 chamber, h p n ing any accidentimparting an [58] Field of Search....219/10.55;200/6l.85,D1G. l,impediment to the human body and simultaneously 2 0O/D1G.2 preventingany interference to other communication appliances. [56] ReferencesCited 6 Claims, 9 Drawing Figures UNITED STATES PATENTS 3,619,53711/1971 Nara et a1 ..219/10.55

7 2\ POWER SOURCE j DETECVUR PATENTEDFEB "6 I975 3.715.553 sum 10F 2 2POWER SOURCE j FIG. 2a

K oA/a 1 NV E NTOR ATTORNEY 1 HIGH-FREQUENCY HEATING EQUIPMENT Thisinvention relates to a high-frequency heating equipment, and moreparticularly to a safety device for high-frequency heating equipmentswherein a detecting section is provided at the handle of a door for aheating chamber and freely opened and shut, whereby when the handle isgrasped this will be detected in the form of an electrical, physical ormagnetic signal by the detecting section, which signal is caused to stopthe high-frequency generator thus to prevent any accident imparting animpediment to the human body as due to an external leakage ofhigh-frequency waves through a port of the heating chamber.

The principal object of the invention is to provide a high-frequencyheating equipment which causes the high-frequency generator to stopimmediately when a hand touches-the handle of the door of the heatingchamber, thereby assuring safety of the human body upon opening the doorand simultaneously preventing any interference to other communicationappliances.

Another object is to provide a high-frequency heating equipment whereina pair or more of electrodes for detection are disposed at the doorhandle made of an electrical insulator, whereby generator is stoppedthrough detection of a change in electrical resistance which occurs whena short-circuit is provided across the detecting electrodes by a part ofthe human body.

Still another object is to provide a high-frequency heating equipmentwherein at least one electrode for detection is disposed at the doorhandle made of an electrical insulator, whereby generator isv stoppedthrough detection of a current which is produced when a part of thehuman body touches the detecting electrode.

A further object is to provide a high-frequency heating equipmentwherein atleast a pair of or more magnetic poles for detection aredisposed at the door handle made of a magnetic insulator, whereby thehighfrequency generator is stopped through the detection of a change inmagnetic reluctance which occurs when 'a short-circuit is providedacross the detecting magnetic poles by a part of the human body.

' A yet further object is to provide a high-frequency heating equipmentwherein a movablepiece moved,

the high-frequency the high-frequency upon grasping the door handle, bya grasping power at that time and a pressure exerted upon the movablepiece is transmitted to a pressure-sensitive element, whereby thehigh-frequency generator is stopped by a signal'from the element.

A still further object isto provide a high-frequency heating equipmentwherein a movable piece moved; upon grasping the door handle, by agrasping power at that time, whereby the high-frequency generator isstopped by effecting the make-and-break of a switch contact with apressure exerted upon the movable piece.

Furtherobjects and features of the invention will be apparent from thefollowing descriptiontaken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a block diagram ofa safety device for a high-frequency heatingequipment, showing an embodiment of thepresent invention; I

FIGS. 2 to 6 show modifications of door handles:

wherein FIGS. 2a and 3a are plan views whileFIGS. 2b

and 3b sectional views, and FIGS. 4 to 6 are sectional views of theessential parts of the modifications; and

FIG. 7 is a diagram of an example of circuit arrangement embodying thesafety device shown in block in FIG. 1.

Referring to FIG. 1 of the accompanying drawings which'shows a preferredembodiment of the invention, a high-frequency generator 1 has a powersource circuit 2 thereof connected to a control circuit 3. This controlcircuit is connected between a series circuit consisting of currentfuses 4 and a power switch 5 and the power circuit 2. A signal detectingsection 6 is disposed at a handle 7 of a freely-openable-and-closabledoor closing a port of a heating chamber into which are radiatedelectric waves from the high-frequency oscillator l. A detector 8detects a signal at the signal detecting section 6 in the form of eitheran electrical or magnetic signal, which is amplified by an amplifier 9and is supplied to the control circuit 3.

More specifically, in the embodiment, when the handle 7 is grasped foropening the door by hand, this will be detected in the form of anelectrical or magnetic signal by means of the detector 8 inclusive ofthe signal detecting section 6. The electrical or magnetic signaldetected is amplified by the amplifier 9 and is fed to the controlcircuit 3. Then, this circuit is opened, whereby power supply to thepower circuit 2 of the highfrequency generator 1 is interrupted therebyto stop the generator 1 from radiating electric waves.

Accordingly, upon grasping the handle 7 by hand, the oscillation fromthe high-frequency generator 1 is ceased. Hence even when the handle 7is successively. drawn to open the lid of the heating chamber, therewill be eliminated the fear of leakage of the electric waves.

FIGS. 2 to 6 are views of concrete constructions for the signaldetecting section 6 which is equipped at the handle 7 in the aboveembodiment. In the construction of FIGS. 2a and 2b, the handle 7a formedof an electrically insulating material is provided with an electrode 10for detection which is made of metal. A current produced when a handtouches the detecting electrode 10 is detected in the form of anelectrical signal by the detector 8, and'is amplifiedby the amplifier 9to be fed to the control circuit 3, thereby interrupting the powersupply to the power circuit 2 of the high-frequency oscillator 1-. v

In FIGS. 3a and 3b, the handle 7b made of metal is provided with amovable pressing piece 12 through a partition wall member 1 l formed ofan insulator. In the partition wall member ll, a pressure-sensitiveelement 14 is disposed upon which a pressure is exerted by the movablepressing piece 12 which moves against the bias of a spring 13 upongrasping the handle 7b.

. More specifically, when the handle 7b is grasped by hand, the movablepressing member 12 will be pressed against the spring 13 to impart apressure to the pressure-sensitive element 14. Then, the element 14 hasits electrical constant changed, and the detectorB in FIG. 1 is causedtosense this change in the form of an electrical signal.

Referring to FIG. 4, the handle 7chas two conductive electrodes 16 and17, along with an intermediate member 15 disposed therebetween and madeof an introdes l6 and 17 of this handle 7c, the resistance across theseelectrodes will vary. The variation is detected in the form of anelectrical signal, and operation is effected by the circuit arrangementshown in FIG. 1.

The handle 7d in FIG. is provided with magnetic poles and 21 fordetection which have an electromagnetic coil 19 disposed in amagnetically insulating material 18, and with a moving iron piece 22which can get into a space between the two magnetic poles.

When a hand touches this handle 7d the moving iron piece 22 will bebrought against the bias of a spring (not shown) into the space betweenthe magnetic poles 20 and 21 to change the magnetic reluctance. This isdetected by the detector 8 in FIG. 1, and is used as a signal.

FIG. 6 refers to the case in which the metal-made handle 7 is per semade an electrode 23 for detection More'specifically, with thestabilized power source, a

constant-voltage circuit consisting of resistors R,, R and a varistor Vris connected to an AC power source, and an output amplified and smoothedby a rectifier unit D, and a capacitor C, appears across terminals a Iand b. These terminals a and b are connected to B- power supply circuitsofthe detector 8, the control circuit 3 and the amplifier 9. Thedetector 8 has the values of its resistor R resistor R and capacitor Cdetermined such that an electrical signal appearing at the detectingelectrode 10 of the handle 7 may be detected as a change in the currentor voltage across the terminals a and c. Namely, in case the electrode10 for detection is disposed at the handle 7 as in FIG. 2, the elementsare set at constants at which there is efficiently detected the currentproduced when a hand touches the detecting electrode 10. In this case,the resistor R, is adjusted in value so as to establish a current valueto the extent that no danger exists upon touching the detectingelectrode 10 by hand.

In the case of the handle 7 shown in FIG. 3, the circuit constants ofthe detector may be set such that an electrical signal sensed by thepressure-sensitive element 14 or a spring switch may be efficientlyinduced in the form of a change in the current or voltage across theterminals a and c.

The amplifier 9 amplifies the change in the current or. voltageoccurring across the terminals a and c, by means of transistors Q, and Qand causes the amplified current to flow across the terminals b and c.The transistor 0, is connected through a resistor R, to the B-powersupply.

The current or voltage detected across the terminals a and c renders thetransistor Q, conductive, so voltages across a capacitor C and aresistor R drop, and a voltage across terminals d and a also dropsthrough a rectifier D Accordingly the base-emitter potential differenceof the transistor 0 is reduced resulting in the conduction of thetransistor 0,, whereby this transistor amplifies the detected current orvoltage across the terminals a and c.

The control circuit 3 has an operating circuit which consists of acontrol switch S, and a variable resistor R The control switch S, isconnected in series with a timer switch S for cooking which is attachedto the electronic heating equipment, with a door switch S, which isopened and closed in interlocking relation to the opening and closure ofthe door of the heating chamber, and with the like, and is connected toan operating coil of an electromagnetic switch S, which in turn isconnected to the power circuit 2 of the highfrequency generator 1.

When a change in potential occurs across the terminals d and a, thetransistor 0 becomes conductive and the control switch S, is broughtinto the open state, with the result that current will be prevented fromflowing through the operating coil of the electromagnetic switch S,connected to the power circuit 2 of the highfrequency oscillator I, thusopening the electromagnetic switch 8,. Consequently, the high-frequencygenerator 1 stops oscillation.

In addition to the preferred example shown in FIG. 7, there may beconsidered the combination of the detector 8, amplifier 9 and controlcircuit 3; the combination of the circuits 8 and 3; a case in which thedetector 8 self-contains a switch thereby per se constituting thecontrol circuit 3; and so on, where it is intended to cease theoscillation of the high-frequency generator 1 by means of an electricalor magnetic signal occurring at the handle 7 of the door of thehigh-frequency heating apparatus and using the stabilized power circuit25, detector 8, amplifier 9 and control circuit 3.

For example, if a Darlington circuit is employed for the detector 8 anda Schmitt circuit for the amplifier 9, then stabilized accuracy will beobtained.

Furthermore, there is considered a method wherein the control circuit isintegrally provided with the control switch S, and the electromagneticswitch S, which is connected to the power circuit 2 of thehigh-frequency generator 1, thereby operating by means of the amplifiedcurrent across the terminals d and a the electromagnetic switch which isdirectly connected to the power source of the high-frequencygenerator 1. Yet furthermore, it is possible to use for the controlcircuit 3 a switching element other than the electromagnetic switch 8,,e.g. a unidirectional three-terminal thyristor or the like. It is alsopossible to employ a spring switch as the operating switch for the powersupply of the high-frequency generator 1.

In addition, numeral 26 in FIG. 7 designates an actuating switch of theheater. When the actuating switch 26 is pressed to be closed under theopen door state, then current will be caused to flow through thecircuits of the operating coils of the switches 8,, S S and theelectromagnetic switch S Thereafter, even if the pressing force isremoved from the actuating switch 26, the electromagnetic switch S, willoperate. The switch 26 may be dispensed with, and at that time a leadwire 27 connecting one end of the operating coil to one end of the powercircuit 2 shall be removed.

We claim:

1. A high-frequency heating equipment comprising a high-frequencygenerator, a heating chamber for heating materials to be cooked by meansof high-frequency waves produced by said high-frequency generator, adoor disposed at a front port of said heating chamber so as to be freelyopened and shut, a handle provided with a detecting section fordetecting as an external signal a contact thereon of the human body, anda control circuit to amplify the signal detected by said handle and tocontrol the make-and-break of a power circuit of said high-frequencygenerator, whereby the contact of the human body onto said handle causessaid control circuit to operate through said detecting section prior toopening said door.

2. A high-frequency heating equipment according to claim 1, wherein saiddetecting section comprises an electrode for receiving a very smallcurrent therethrough from said human body to ground due to electricityinduced in said body, said small current being amplified by said controlcircuit for controlling the make-and-break of said power circuit.

3. A high-frequency heating equipment according to claim 1, wherein saidhandle of said door is provided with at least one pair of electrodes fordetection connected to a detector circuit, said pair of electrodes beingadapted to cause said detector circuit to produce a signal due tovariations in the resistance between them when short-circuited by thehuman body, said signal being amplified by said control circuit forcontrolling the make-and-break of said power circuit.

4. A high-frequency heating equipment according to claim 1, wherein saidhandle of said door is provided with at least one pair of magnetic polesand with a movable member of a magnetic substance disposed between thesemagnetic poles for detection, whereby a change in magnetic reluctance isdetefted which is produced when said movable member is located betweensaid magnetic poles by a part of the human body.

5. A high-frequency heating equipment according to claim 1, wherein saidhandle of said door is provided with a movable piece which moves bymeans of a grasping power when said handle is grasped and with apressure-sensitive element, whereby a pressure exerted on said movablepiece is detected by said pressure-sensitive element.

6. A high-frequency heating equipment comprising a high-frequencygenerator, a heating chamber for heating materials to be cooked by meansof high-frequency waves produced by said high-frequency generator, adoor disposed at a front port of said heating chamber so as to be freelyopened and shut, a handle self-containing a make-and-break contact, anda control circuit to control the make-and-break of a power circuit ofsaid high-frequency generator through the operation of saidmake-and-break contact, whereby the action of grasping said handle uponopening said door causes said control circuit to operate.

1. A high-frequency heating equipment comprising a highfrequencygenerator, a heating chamber for heating materials to be cooked by meansof high-frequency waves produced by said highfrequency generator, a doordisposed at a front port of said heating chamber so as to be freelyopened and shut, a handle provided with a detecting section fordetecting as an external signal a contact thereon of the human body, anda control circuit to amplify the signal detected by said handle and tocontrol the make-and-break of a power circuit of said high-frequencygenerator, whereby the contact of the human body onto said handle causessaid control circuit to operate through said detecting section prior toopening said door.
 1. A high-frequency heating equipment comprising ahigh-frequency generator, a heating chamber for heating materials to becooked by means of high-frequency waves produced by said high-frequencygenerator, a door disposed at a front port of said heating chamber so asto be freely opened and shut, a handle provided with a detecting sectionfor detecting as an external signal a contact thereon of the human body,and a control circuit to amplify the signal detected by said handle andto control the make-and-break of a power circuit of said high-frequencygenerator, whereby the contact of the human body onto said handle causessaid control circuit to operate through said detecting section prior toopening said door.
 2. A high-frequency heating equipment according toclaim 1, wherein said detecting section comprises an electrode forreceiving a very small current therethrough from said human body toground due to electricity induced in said body, said small current beingamplified by said control circuit for controlling the make-and-break ofsaid power circuit.
 3. A high-frequency heating equipment according toclaim 1, wherein said handle of said door is provided with at least onepair of electrodes for detection cOnnected to a detector circuit, saidpair of electrodes being adapted to cause said detector circuit toproduce a signal due to variations in the resistance between them whenshort-circuited by the human body, said signal being amplified by saidcontrol circuit for controlling the make-and-break of said powercircuit.
 4. A high-frequency heating equipment according to claim 1,wherein said handle of said door is provided with at least one pair ofmagnetic poles and with a movable member of a magnetic substancedisposed between these magnetic poles for detection, whereby a change inmagnetic reluctance is detefted which is produced when said movablemember is located between said magnetic poles by a part of the humanbody.
 5. A high-frequency heating equipment according to claim 1,wherein said handle of said door is provided with a movable piece whichmoves by means of a grasping power when said handle is grasped and witha pressure-sensitive element, whereby a pressure exerted on said movablepiece is detected by said pressure-sensitive element.